ABSTRACT

Stegosaurs were not built for rapid locomotion. Instead of fleeing from predators, they probably used their spiked tails as 'thagomizers' for defense. Kinetic/dynamic modeling in a computer-aided engineering program allows either using prescribed joint motions to determine joint forces or torque input models that deliver accelerations and moment of inertia of the tail tip spikes. Prescribed motion models based on a CAD range of motion analysis of Kentrosaurus and motions observed in extant long-tailed reptiles give results consistent with those of models using torque values calculated from detailed CAD reconstruction of muscle cross sections and moment arms. Both indicate that the tail of Kentrosaurus was a dangerous weapon, capable of inflicting painful slashing injuries and debilitating penetrating trauma, even on large theropods, across a large portion of its motion range. Continuous rapid motion was at least sufficient for the spikes to slash open the integument or penetrate soft tissues and fracture ribs or facial bones, while aimed whiplash blows may have had sufficient energy to fracture sturdy longbones.

Heinrich Mallison. Museum für Naturkunde - Leibniz Institute for Research on Evolution and Biodiversity at the Humboldt University Berlin, Berlin, Germany